Drug delivery of temozolomide for systemic based treatment of cancer

ABSTRACT

The present invention relates to methods of drug delivery for the treatment of a condition or disease, such as cancer. In one embodiment, the invention provides a method of preparing a multifunctional nanoconjugate of temozolomide (TMZ) by conjugating TMZ in its hydrazide form to a polymalic acid platform. In another embodiment, the polymalic acid platform is conjugated to a monoclonal antibody to transferrin receptor, a trileucine (LLL) moiety, and/or a polyethylene glycol (PEG) moiety. The present invention relates to methods of drug delivery for the treatment of a condition or disease, such as cancer. In one embodiment, the invention provides a method of preparing a multifunctional nanoconjugate of temozolomide (TMZ) by conjugating TMZ in its hydrazide form to a polymalic acid platform. In another embodiment, the polymalic acid platform is conjugated to a monoclonal antibody to transferrin receptor, a trileucine (LLL) moiety, and/or a polyethylene glycol (PEG) moiety.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to International Application No.PCT/US2010/059919, filed Dec. 10, 2010, which claims the benefit of U.S.Provisional Patent Application No. 61/285,495, filed Dec. 10, 2009 whichare incorporated by reference as if fully set forth.

GOVERNMENT RIGHTS

The U.S. Government has a paid-up license in this invention and theright in limited circumstances to require the patent owner to licenseothers on reasonable terms as provided for by the terms of Grant No. RO1CA123495 awarded by the National Institutes of Health.

BACKGROUND

All publications herein are incorporated by reference to the same extentas if each individual publication or patent application was specificallyand individually indicated to be incorporated by reference. Thefollowing description includes information that may be useful inunderstanding the present invention. It is not an admission that any ofthe information provided herein is prior art or relevant to thepresently claimed invention, or that any publication specifically orimplicitly referenced is prior art.

Malignant gliomas are the most common (60-70%) of all CNS/brain tumors.Annually there are approximately 5 cases of malignant gliomas per100,000 people and over 14,000 new cases are diagnosed each year in theUnited States (1, 2). Surgery remains the standard therapy for primarybrain tumors. Although surgery may be combined with radiation therapyand/or followed with chemotherapy to destroy remaining cancer cells,patients still have a poor survival advantage (3-5). In recent years,the prodrug Temozolomide (TMZ, TEMODAR), for example, which undergoesspontaneous conversion to the active alkylating agent, has emerged as apotent chemotherapeutic agent (6). In combination with radiotherapy, ithas been shown to substantially increase median survival compared withradiotherapy alone (7). However, as with many potential chemotherapeuticagents, TMZ has considerable toxicity, which prevents therapeutic dosageincrease. Moreover, another limiting factor of TMZ treatment is tumorresistance to the drug (8-10).

Thus, there is a need in the art for novel drug delivery systems thathave tumor targeting, increased solubility, enhanced accumulation insolid tumors, decreased general toxicity, increased maximum tolerateddoses, circumvention of multidrug resistance and enhanced apoptosisinduction.

SUMMARY OF THE INVENTION

Various embodiments include a drug delivery system comprising apolymalic acid platform conjugated to a pro-drug, and one or moretargeting antibodies, a trileucine (LLL) moiety, and/or a polyethyleneglycol (PEG) moiety. In another embodiment, the pro-drug comprises atherapeutically effective amount of a compound of the formula:

or a pharmaceutical equivalent, analog, derivative and/or salt thereof.In another embodiment, the one or more targeting antibodies is amonoclonal antibody to transferrin receptor (TfR). In anotherembodiment, the polymalic acid platform comprises a compound of theformula:

or a pharmaceutical equivalent, analog, derivative and/or salt thereof.In another embodiment, the one or more targeting antibodies is aanti-TfR humanized antibody. In another embodiment, the anti-TfRhumanized antibody is used for active transport to a tumor. In anotherembodiment, one or more targeting antibodies is an anti-TfR mousemonoclonal antibody and/or an anti-TfR human monoclonal antibody.

Other embodiments include a pharmaceutical composition, comprising atherapeutically effective amount of a multifunctional nanoconjugate oftemozolmide (TMZ), and a pharmaceutically acceptable carrier. In anotherembodiment, the multifunctional nanoconjugate of TMZ is a compound ofthe formula:

or a pharmaceutical equivalent, analog, derivative and/or salt thereof.In another embodiment, the multifunctional nanoconjugate of TMZ is acompound of the formula:

or a pharmaceutical equivalent, analog, derivative and/or salt thereof.

Other embodiments include a method of treating a disease and/orcondition in an individual, comprising administering a therapeuticallyeffective dosage of a drug delivery system comprising a polymalic acidplatform conjugated to a pro-drug, and one or more targeting antibodies,a trileucine (LLL) moiety, and/or a polyethylene glycol (PEG) moiety tothe individual, and treating the individual. In another embodiment, thepro-drug comprises a therapeutically effective amount of a compound ofthe formula:

or a pharmaceutical equivalent, analog, derivative and/or salt thereof.In another embodiment, the therapeutically effective amount of thecompound of the formula:

or a pharmaceutical equivalent, analog, derivative and/or salt thereof,is between 1 mg/kg and 10 mg/kg concentration. In another embodiment,the targeting antibody is a monoclonal antibody to transferrin receptor(TfR). In another embodiment, the polymalic acid platform comprises acompound of the formula:

or a pharmaceutical equivalent, analog, derivative and/or salt thereof.In another embodiment, the drug delivery system comprises a compound ofthe formula:

or a pharmaceutical equivalent, analog, derivative and/or salt thereof.In another embodiment, the drug delivery system comprises a compound ofthe formula:

or a pharmaceutical equivalent, analog, derivative and/or salt thereof.In another embodiment, the drug delivery system is administered to theindividual intravenously. In another embodiment, the drug deliverysystem is administered to the individual at a concentration of about 4mg/kg. In another embodiment, the drug delivery system is administeredto the individual by direct injection and/or orally. In anotherembodiment, the drug delivery system is administered to the individualat a concentration of 75 mg/m². In another embodiment, the individual isa human. In another embodiment, the individual is a mouse and/or rat. Inanother embodiment, the drug delivery system comprises an anti-TfR mousemonoclonal antibody and/or an anti-TfR human monoclonal antibody. Inanother embodiment, the drug delivery system comprises an anti-TfRhumanized antibody.

Various embodiments include a method of preparing a drug deliverysystem, comprising:

conjugating a compound of the formula:

or a pharmaceutical equivalent, analog, derivative and/or salt thereof,to an ionic polymalic acid. In another embodiment, the ionic polymalicacid comprises one or more targeting antibodies, a trileucine (LLL)moiety, and/or a polyethylene glycol (PEG) moiety. In anotherembodiment, the ionic polymalic acid comprises an anti-TfR humanizedantibody for transporting to a tumor.

Other features and advantages of the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings, which illustrate, by way of example, variousembodiments of the invention.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts, in accordance with an embodiment herein, schematicpresentation of the drug delivery system.

FIG. 2 depicts, in accordance with an embodiment herein, liposomalleakage assay: a) Liposome leakage of P/LOEt and P/LLL conjugates, b)Liposome leakage of P/LLL/TMZH and P/PEG/LLL/TMZH conjugates. Percentagerefers to ratio of pendant —COOH conjugated (total PMLA pendant —COOH is100%). % Leakage compared to complete leakage in the presence of thedetergent TRITON X-100 0.25% (v/v).

FIG. 3 depicts, in accordance with an embodiment herein, nanoconjugatedegradation in PBS and human plasma. Degradation of conjugateP/LLL(40%)TMZH(17%) in PBS and human plasma at 4° C. and 37° C. studiedby relative changes in molecular size indicated by column retentiontimes (% molecular weights) of SEC-HPLC and hydrodynamic diametermeasured by a particle and molecular size analyzer ZETASIZER. 100%refers to the size at time zero.

FIG. 4 depicts, in accordance with an embodiment herein, cell viabilityof nanoconjugate with LLL: Effects on cell viability of TMZ, P/LLL(40%),P/PEG(2%)/TMZH(30%) and P/LLL(40%)/TMZH(17%) on a) U87MG, b) T98G, c)MDA-MB-231 and d) MDA-MB-468 cells. Nanoconjugate P/LLL(40%) withoutdrug was used as a control for the conjugate P/LLL(40%)/TMZH(17%) withdrug and contains equivalent amount of polymer backbone. NanoconjugateP/PEG(2%)/TMZH(30%) even with high loading of TMZH but without LLLendosome escape unit was only marginally effective. P/LLL(40%)/TMZH(17%)was the most effective nanoconjugate.

FIG. 5 depicts, in accordance with an embodiment herein, cell viabilityof nanoconjugate with LOEt: Effects on cell viability of TMZ,P/PEG(2%)/LOEt(40%) and P/PEG(2%)/LOEt(40%)/TMZH(17%) on a) U87MG and b)T98G cells. Nanoconjugate P/PEG(2%)/LOEt(40%) without drug was used as acontrol for the conjugate P/PEG(2%)/LOEt(40%)/TMZH(17%) with drug andcontains equivalent amount of polymer backbone.

FIG. 6 depicts, in accordance with an embodiment herein, cell viabilityof LLL nanoconjugates with antibody: Effects on cell viability of TMZ,P/PEG(2%)/LLL(40%)/TMZH(17%), P/PEG(2%)/LLL(40%)/TMZH(17%)/IgG(0.25%),P/PEG(2%)/LLL(40%)/TMZH(17%)/HuTfR mAb(0.25%) on a) U87MG and b) MDA-MB468 cells. Conjugation of HuTfR mAb increased the activity of drug onU87MG cell line, whereas no such effect was observed on MDA-MB-468.

FIG. 7 depicts, in accordance with an embodiment herein, druginternalization into cultured human glioma U87MG cells by confocalmicroscopy: a) 1 h incubation with fluorescently labeled conjugateP/PEG(2%)/LLL(40%)TMZH(17%)/Alx680(1%). The location of conjugate isindicated by fluorescence; b) phase contrast; c) 1 h incubation withfluorescently labeled conjugate P/PEG(2%)/LLL(40%)TMZH(17%)/HuTfRmAb(0.25%)/Alx680(1%). The location of conjugate is indicated byfluorescence; d) phase contrast.

FIG. 8 depicts, in accordance with an embodiment herein, pH-dependentconversion of TMZ to metabolites,5-(3-methyltriazen-1-yl)imidazole-4-carboxamide (MTIC),4-amino-5-imidazole-carboxamide (AIC), methyldiazonium ion and DNAmethylation (6)

FIG. 9 depicts, in accordance with an embodiment herein, (a)temozolomide (TMZ) and (b) temozolomide hydrazide (TMZH).

FIG. 10 depicts, in accordance with an embodiment herein, syntheticstrategy for LOEt conjugates containing TMZH.

FIG. 11 depicts, in accordance with an embodiment herein, syntheticstrategy for LLL conjugates containing TMZH.

FIG. 12 depicts, in accordance with an embodiment herein, comparison oftumor growth rate between treated and untreated animals.

FIG. 13 depicts, in accordance with an embodiment herein, comparison oftumor volume between treated and untreated animals.

DESCRIPTION OF THE INVENTION

All references cited herein are incorporated by reference in theirentirety as though fully set forth. Unless defined otherwise, technicaland scientific terms used herein have the same meaning as commonlyunderstood by one of ordinary skill in the art to which this inventionbelongs. Singleton et al., Dictionary of Microbiology and MolecularBiology 3^(rd) ed., J. Wiley & Sons (New York, N.Y. 2001); March,Advanced Organic Chemistry Reactions, Mechanisms and Structure 5^(th)ed., J. Wiley & Sons (New York, N.Y. 2001); and Sambrook and Russel,Molecular Cloning: A Laboratory Manual 3^(rd) ed., Cold Spring HarborLaboratory Press (Cold Spring Harbor, N.Y. 2001), provide one skilled inthe art with a general guide to many of the terms used in the presentapplication.

One skilled in the art will recognize many methods and materials similaror equivalent to those described herein, which could be used in thepractice of the present invention. Indeed, the present invention is inno way limited to the methods and materials described.

As used herein, the term “TMZ” also refers to temozolomide, and is acompound of the formula:

or a pharmaceutical equivalent, analog, derivative and/or salt thereof.

As used herein, the term “TMZH” also refers to temozolomide hydrazide,and is a compound of the formula:

or a pharmaceutical equivalent, analog, derivative and/or salt thereof.

As used herein, the term “PMLA” is an abbreviation for poly(β-L-malicacid), and is a compound of the formula:

or a pharmaceutical equivalent, analog, derivative and/or salt thereof.

As used herein, the term “HuTfR mAb” means anti-human transferrinreceptor monoclonal antibody.

As used herein, the term “LOEt” means L-leucine ethyl ester.

As used herein, the term “LLL” is an abbreviation ofL-Leu-(L-Leu)-(L-Leu).

As used herein, the term “Alex680” means the fluorescent dye ALEXA FLUOR680 C2 maleimide.

As used herein, the term “PMLA-LLL” includes PMLA containing LLL, whichis conjugated by amide bond involving the N-terminal —NH₂.

As used herein, the term “PMLA-LLL40%” includes PMLA containing 40% ofpendant carboxylates (100%) conjugated by amide bond involving theN-terminal —NH₂ of oligopeptide trileucine LLL.

As used herein, the term “Polycefin” is a general name for therapeuticnanoconjugates based on polymalic acid for drug delivery. It may containmultifunctional components, such as a drug, a targeting moiety, and anendosome escaping unit.

As disclosed herein, temozolomide (TMZ) is a pro-drug releasing a DNAalkylating agent that may treat glial tumors when combined withradiation. TMZ is toxic and therapeutic dosages are limited by severeside effects. Targeted delivery is thus needed to improve efficiency andreduce non-tumor tissue toxicity. The inventors synthesizedmultifunctional targetable nanoconjugates of TMZ hydrazide using apoly(β-L-malic acid) platform, which contained a targeting monoclonalantibody to transferrin receptor (TfR), trileucine (LLL) forpH-dependent endosomal membrane disruption, and PEG for protection.

In one embodiment, the present invention provides a compositioncomprising a multifunctional nanoconjugate of temozolomide (TMZ), or apharmaceutical equivalent, analog, derivative, or salt thereof. Inanother embodiment, the multifunctional nanoconjugate of TMZ, or apharmaceutical equivalent, analog, derivative, or salt thereof,comprises TMZ conjugated to an ionic polymalic acid. In anotherembodiment, the TMZ, or pharmaceutical equivalent, analog, derivative,or salt thereof comprises TMZ hydrazide. In another embodiment, theionic polymalic acid comprises poly(β-L-malic acid). In anotherembodiment, the poly(β-L-malic acid) contains a targeting moiety, apH-dependent endosome membrane disruption moiety, and/or a PEG moiety.In another embodiment, the targeting moiety comprises a targetingmonoclonal antibody to transferrin receptor. In another embodiment, theendosome membrane disruption moiety comprises trileucine (LLL) and/orL-leucine ethyl ester (LoEt).

As further disclosed herein, the water-soluble TMZ nanoconjugates hadhydrodynamic diameters in the range of 6.5 to 14.8 nm and ζ potentialsin the range of −6.3 to −17.7 mV. 50% degradation in human plasma wasobserved in 40 h at 37° C. TMZ conjugated with polymer had a half-lifeof 5-7 h, compared with 1.8 h for free TMZ. The strongest reduction ofhuman brain and breast cancer cell viability was obtained by versions ofTMZ nanoconjugates containing LLL and anti-TfR antibody. TMZ-resistantcancer cell lines were sensitive to TMZ nanoconjugate treatment.TMZ-polymer nanoconjugates entered the tumor cells by receptor-mediatedendocytosis, effectively reduced cancer cell viability, and can be usedfor targeted tumor treatment.

In one embodiment, the present invention provides a method of treating acancer by administering a therapeutically effective dosage of acomposition comprising a multifunctional nanoconjugate of temozolomide(TMZ), or a pharmaceutical equivalent, analog, derivative, or saltthereof, to an individual. In another embodiment, the multifunctionalnanoconjugate of temozolomide (TMZ), or a pharmaceutical equivalent,analog, derivative, or salt thereof, is administered to the individualsystemically. In another embodiment, the multifunctional nanoconjugateof temozolomide (TMZ), or a pharmaceutical equivalent, analog,derivative, or salt thereof, is administered to the individualsystemically via intravenous administration. In another embodiment, themultifunctional nanoconjugate of temozolomide (TMZ), or a pharmaceuticalequivalent, analog, derivative, or salt thereof, is administered to theindividual orally and/or via direct injection. In another embodiment,the cancer is brain cancer. In another embodiment, side effects to theindividual are minimized due to less free diffusion of the TMZ, whereinthe TMZ is conjugated to a polycefin platform. In another embodiment,side effects to the individual are minimized to the individual due tospecific tumor treatment and targeting resulting a homing device moietyof the multifunctional nanoconjugate of TMZ.

In conjunction with various embodiments described herein, the inventorshave successfully conjugated TMZ via the hydrazide bond to the highlynegatively charged PMLA that renders the prodrug no longer diffusiblethrough membranes. This allows a highly more potent and effectivedelivery of TMZ (or other drugs). Unlike the conjugated TMZ form, themore traditional orally applied TMZ for treating human gliomas has thepotency to be distributed all over the entire organism. Afterpenetration of the lipophilic prodrug through membranes into thecytoplasm of recipient cells it will be activated by the hydrolyticmechanism described herein. The active drug is then ready to methylateproteins and especially DNA, guanine at N7 position, followed bymethylation of adenine at the O3 position and of guanine at the O6position (33). Failure of repair will drive these cells into apoptosis.Hydrolytic activation of the prodrug at sites other than the cytoplasmis inefficient due to the fact that the cationic methyl diazonium likeany other charged molecule cannot passively penetrate membranes.However, in contrast, by conjugating TMZ and rendering the prodrug nolonger diffusible through the membranes, the active methyl diazoniumcation can only be generated from the nanodrug. Free passive diffusionof the PMLA conjugate into recipient cells is highly unlikely because ofits high negative charge, and generation of active drug outside thecytoplasm would not be effective due to its own intrinsic charge.Therefore, the nanodrug can only give rise to nucleic acid methylationif it is internalized into the cytoplasm of recipient cells.

As further disclosed herein, a multifunctional nanoconjugate, or apharmaceutical equivalent, analog, derivative, or salt thereof, wassynthesized with PMLA as the platform and prodrug TMZ in its hydrazideform, H₂N-Leu-Leu-LeuOH (LLL) or NH₂-LeuOEt (LOEt) for disruption ofendosomal membrane, antibodies for targeting, and PEG against resorptionand enzyme degradation.

In one embodiment, the present invention provides a method of preparinga multifunctional nanoconjugate of temozolomide (TMZ), or apharmaceutical equivalent, analog, derivative, or salt thereof byconjugating TMZ in its hydrazide form to a polycefin platform. Inanother embodiment, the multifunctional nanoconjugate of TMZ is preparedby the following steps, or a combination thereof: (1) chemicalactivation of the PMLA pendant carboxyl groups forming the NHS-ester andsubsequently the nucleophilic replacement by forming stable amide bonds;(2) conjugation of antibodies via thioether bond formation, wherebecause of the PMLA chain length inhomogeneity, an excess of mAb ischosen in order to increase the likelihood that at least one moleculewas conjugated with each polymer chain; (3) conjugation with LLL, wherebecause the amount of 40% of carboxyl groups conjugated with LLL formost efficient membrane disruption activity limits the amount of TMZHconjugation to 17%, in order to increase the amount of TMZH loading, (4)carboxyl activation is repeated after conjugation with LLL, (5) beforeconjugation with TMZH.

The present invention is also directed to a kit for materials forpreparing a multifunctional nanoconjugate of temozolomide (TMZ), as wellas the administration of the multifunctional nanoconjugate of TMZ to theindividual, and may include a polymalic acid platform, PEG forprotection, antibodies for targeting, TMZ molecules in hydrazide form,COOH for solubility in aqueous solvent, and tracking molecules such asthe fluorescent dye ALMA FLUOR 680, and combinations thereof. The kit isan assemblage of materials or components, including at least one of theinventive compositions.

The exact nature of the components configured in the inventive kitdepends on its intended purpose. For example, some embodiments areconfigured for the purpose of treating brain cancer or drug delivery inmammalian subjects, such as, but not limited to, human subjects, farmanimals, domestic animals, and laboratory animals.

Instructions for use may be included in the kit. “Instructions for use”typically include a tangible expression describing the technique to beemployed in using the components of the kit to effect a desired outcome,such as to prepare a multifunctional nanoconjugate of TMZ and to delivera therapeutically effective dosage of TMZ to an individual. Optionally,the kit also contains other useful components, such as, diluents,buffers, pharmaceutically acceptable carriers, syringes, catheters,applicators, pipetting or measuring tools, bandaging materials or otheruseful paraphernalia as will be readily recognized by those of skill inthe art.

The materials or components assembled in the kit can be provided to thepractitioner stored in any convenient and suitable ways that preservetheir operability and utility. For example the components can be indissolved, dehydrated, or lyophilized form; they can be provided atroom, refrigerated or frozen temperatures. The components are typicallycontained in suitable packaging material(s). As employed herein, thephrase “packaging material” refers to one or more physical structuresused to house the contents of the kit, such as inventive compositionsand the like. The packaging material is constructed by well knownmethods, preferably to provide a sterile, contaminant-free environment.The packaging materials employed in the kit are those customarilyutilized in preparing a nanoconjugate. As used herein, the term“package” refers to a suitable solid matrix or material such as glass,plastic, paper, foil, and the like, capable of holding the individualkit components. Thus, for example, a package can be a glass vial used tocontain suitable quantities of an inventive composition containing asolution of multifunctional nanoconjugate of TMZ or components thereof.The packaging material generally has an external label which indicatesthe contents and/or purpose of the kit and/or its components.

In various embodiments, the present invention provides pharmaceuticalcompositions including a pharmaceutically acceptable excipient alongwith a therapeutically effective amount of Polycefin-LLL.“Pharmaceutically acceptable excipient” means an excipient that isuseful in preparing a pharmaceutical composition that is generally safe,non-toxic, and desirable, and includes excipients that are acceptablefor veterinary use as well as for human pharmaceutical use. Suchexcipients may be solid, liquid, semisolid, or, in the case of anaerosol composition, gaseous.

In various embodiments, the pharmaceutical compositions according to theinvention may be formulated for delivery via any route ofadministration. “Route of administration” may refer to anyadministration pathway known in the art, including but not limited to anintravenous injection, aerosol, nasal, oral, transmucosal, transdermalor parenteral. “Parenteral” refers to a route of administration that isgenerally associated with injection, including intraorbital, infusion,intraarterial, intracapsular, intracardiac, intradermal, intramuscular,intraperitoneal, intrapulmonary, intraspinal, intrasternal, intrathecal,intrauterine, intravenous, subarachnoid, subcapsular, subcutaneous,transmucosal, or transtracheal. Via the parenteral route, thecompositions may be in the form of solutions or suspensions for infusionor for injection, or as lyophilized powders.

The pharmaceutical compositions according to the invention can alsocontain any pharmaceutically acceptable carrier. “Pharmaceuticallyacceptable carrier” as used herein refers to a pharmaceuticallyacceptable material, composition, or vehicle that is involved incarrying or transporting a compound of interest from one tissue, organ,or portion of the body to another tissue, organ, or portion of the body.For example, the carrier may be a liquid or solid filler, diluent,excipient, solvent, or encapsulating material, or a combination thereof.Each component of the carrier must be “pharmaceutically acceptable” inthat it must be compatible with the other ingredients of theformulation. It must also be suitable for use in contact with anytissues or organs with which it may come in contact, meaning that itmust not carry a risk of toxicity, irritation, allergic response,immunogenicity, or any other complication that excessively outweighs itstherapeutic benefits.

The pharmaceutical compositions according to the invention can also beencapsulated, tableted or prepared in an emulsion or syrup for oraladministration. Pharmaceutically acceptable solid or liquid carriers maybe added to enhance or stabilize the composition, or to facilitatepreparation of the composition. Liquid carriers include syrup, peanutoil, olive oil, glycerin, saline, alcohols and water. Solid carriersinclude starch, lactose, calcium sulfate, dihydrate, terra alba,magnesium stearate or stearic acid, talc, pectin, acacia, agar orgelatin. The carrier may also include a sustained release material suchas glyceryl monostearate or glyceryl distearate, alone or with a wax.

The pharmaceutical preparations are made following the conventionaltechniques of pharmacy involving milling, mixing, granulation, andcompressing, when necessary, for tablet forms; or milling, mixing andfilling for hard gelatin capsule forms. When a liquid carrier is used,the preparation will be in the form of a syrup, elixir, emulsion or anaqueous or non-aqueous suspension. Such a liquid formulation may beadministered directly p.o. or filled into a soft gelatin capsule.

The pharmaceutical compositions according to the invention may bedelivered in a therapeutically effective amount. The precisetherapeutically effective amount is that amount of the composition thatwill yield the most effective results in terms of efficacy of treatmentin a given subject. This amount will vary depending upon a variety offactors, including but not limited to the characteristics of thetherapeutic compound (including activity, pharmacokinetics,pharmacodynamics, and bioavailability), the physiological condition ofthe subject (including age, sex, disease type and stage, generalphysical condition, responsiveness to a given dosage, and type ofmedication), the nature of the pharmaceutically acceptable carrier orcarriers in the formulation, and the route of administration. Oneskilled in the clinical and pharmacological arts will be able todetermine a therapeutically effective amount through routineexperimentation, for instance, by monitoring a subject's response toadministration of a compound and adjusting the dosage accordingly. Foradditional guidance, see Remington: The Science and Practice of Pharmacy(Gennaro ed. 20th edition, Williams & Wilkins PA, USA) (2000).

Typical dosages of an effective delivery of a multifunctionalnanoconjugate of TMZ, or a pharmaceutical equivalent, analog,derivative, or salt thereof, can be in the ranges recommended by themanufacturer where known therapeutic compounds are used, and also asindicated to the skilled artisan by the in vitro responses or responsesin animal models. Such dosages typically can be reduced by up to aboutone order of magnitude in concentration or amount without losing therelevant biological activity. Thus, the actual dosage will depend uponthe judgment of the physician, the condition of the patient, and theeffectiveness of the therapeutic method based, for example, on the invitro responsiveness of the relevant primary cultured cells orhistocultured tissue sample, such as biopsied malignant tumors, or theresponses observed in the appropriate animal models, as previouslydescribed.

As described herein, various embodiments of the invention include thetherapeutically effective delivery of a multifunctional nanoconjugate ofTMZ, or a pharmaceutical equivalent, analog, derivative, or saltthereof, to an individual in treatment of brain cancer. As readilyapparent to one of skill in the art, the invention may be applied to anynumber of targets where it would be beneficial to deliver a drug ormolecule to an individual while decreasing side effects due to less freediffusion and/or targeted delivery. Similarly, any number of conditionsand/or diseases may be beneficially treated and the invention is in noway limited to treatment of brain cancer and/or tumor suppression. Forexample, various embodiments described herein may include the treatmentof HIV and/or AIDS, and any other number of conditions where it isadvantageous to deliver a therapeutically effective dosage of a drug.Finally, as would be readily apparent to one of skill in the art,various molecules and/or drugs may also be delivered, including thedelivery of proteins, and the various embodiments described herein arein no way limited to delivery of TMZ, or its pharmaceutical equivalent,analog, derivative, or salt thereof.

Various embodiments of the invention may also be practiced inconjunction with an overall treatment regimen. For example, as describedherein, various embodiments include the delivery of TMZ by way ofdisruption of the endosome. As readily apparent to one of skill in theart, additional drugs or substances that were previously inactive in theendosome will then become active upon the disruption of the endosome.Thus, various embodiments of the invention may include additional drugsor substances administered to the subject being treated and theinvention is not only limited to drugs and/or molecules covalentlylinked to the scaffold as described herein. Similarly, as readilyapparent to one of skill in the art, various embodiments of theinvention may be used in conjunction with or in combination withadditional therapeutics.

One skilled in the art will recognize many methods and materials similaror equivalent to those described herein, which could be used in thepractice of the present invention. Indeed, the present invention is inno way limited to the methods and materials described. For purposes ofthe present invention, the following terms are defined below.

EXAMPLES

The following examples are provided to better illustrate the claimedinvention and are not to be interpreted as limiting the scope of theinvention. To the extent that specific materials are mentioned, it ismerely for purposes of illustration and is not intended to limit theinvention. One skilled in the art may develop equivalent means orreactants without the exercise of inventive capacity and withoutdeparting from the scope of the invention.

Example 1 General

Temozolomide (TMZ) is a pro-drug releasing a DNA alkylating agent thatmay treat glial tumors when combined with radiation. TMZ is toxic andtherapeutic dosages are limited by severe side effects. Targeteddelivery is thus needed to improve efficiency and reduce non-tumortissue toxicity. The inventors synthesized multifunctional targetablenanoconjugates of TMZ hydrazide using a poly(β-L-malic acid) platform,which contained a targeting monoclonal antibody to transferrin receptor(TfR), trileucine (LLL) for pH-dependent endosomal membrane disruption,and PEG for protection.

As further disclosed herein, the water-soluble TMZ nanoconjugates hadhydrodynamic diameters in the range of 6.5 to 14.8 nm and ζ potentialsin the range of −6.3 to −17.7 mV. 50% degradation in human plasma wasobserved in 40 h at 37° C. TMZ conjugated with polymer had a half-lifeof 5-7 h, compared with 1.8 h for free TMZ. The strongest reduction ofhuman brain and breast cancer cell viability was obtained by versions ofTMZ nanoconjugates containing LLL and anti-TfR antibody. TMZ-resistantcancer cell lines were sensitive to TMZ nanoconjugate treatment.TMZ-polymer nanoconjugates entered the tumor cells by receptor-mediatedendocytosis, effectively reduced cancer cell viability, and can be usedfor targeted tumor treatment.

Example 2 Reagents Used

TMZ was purchased from AK Scientific, Inc. (Mountain View, Calif., USA).TMZ hydrazide (TMZH) was synthesized from TMZ as described (25). Mouseanti-human TfR mAb RVS10 was purchased from Southern Biotech(Birmingham, Ala., USA). PMLA (100 kDa; polydispersity 1.3; hydrodynamicdiameter 6.6 nm; ζ potential −22.5 mV, pH 7.5 at 25° C.) was obtainedfrom culture broth of Physarum polycephalum as described (26).mPEG₅₀₀₀-amine and maleimide-PEG₃₄₀₀-maleimide were obtained from LaysanBio, Inc. (Arab, Ala., USA). NH₂-Leu-OEt (LOEt) and NH₂-Leu-Leu-Leu-OH(LLL) were purchased from Bachem Americas, Inc. (Torrance, Calif., USA).Egg yolk and phosphatidylcholine from Fluka (Buchs, Switzerland).3-(2-Pyridyldithio)-propionate (PDP) was synthesized as described (27).The fluorescent dye ALMA FLUOR 680 C2 maleimide (Alex680) was fromInvitrogen Corporation (Carlsbad, Calif., USA). Unless otherwiseindicated, all chemicals and solvents of highest purity were purchasedfrom Sigma-Aldrich (St. Louis, Mo.) USA.

Example 3 Analytical Methods for Chemical Synthesis

The conjugation reaction of PMLA with PEG, TMZH, LLL and LOEt wasfollowed by thin layer chromatography (TLC) on precoated silica gel 60F254 aluminum sheets (Merck, Darmstadt, Germany) and visualization ofspots by UV light and/or by ninhydrin staining. The concentration offree or conjugated TMZH was monitored by reading A₃₂₈ and using knownamounts of TMZ or TMZH standards. Size exclusion chromatography wasperformed on LACHROM ELITE, an analytical High Performance LiquidChromatograph (HPLC) system with Diode Array Detector L 2455 (Hitachi,Pleasanton, Calif., USA), and M_(w) was measured using BioSep-SEC-S 3000(300×7.80 mm) (Phenomenex, Torrance, Calif., USA) with 50 mM sodiumphosphate buffer pH 6.8 and polystyrene sulfonates as molecular weightstandards. Thiol residues attached to PMLA were assayed by the method ofEllman. Enzyme-linked immunosorbent assay (ELISA) was used to determinethe functional activity of conjugated antibody using a Protein DetectorELISA Kit (KPL, Inc., Gaithersburg, Mass., USA). Human TfR ectodomainused as antigen was obtained from Protein Expression Center, CaliforniaInstitute of Technology, Pasadena, USA.

Example 4 Syntheses of Nanoconjugates

A variety of conjugates were synthesized in order to examine the effectof each conjugated functional group on membrane disruption and cellviability. Two membrane disrupting units were examined for theirusefulness in endosome escape: LOEt and LLL. The synthetic strategiesfor the nanoconjugates containing the LOEt endosomal escape unit aresummarized in FIG. 10 and for those containing LLL endosomal escapeunit, in FIG. 11. Conjugates containing different amounts of TMZH weresynthesized by analogous methods.

Example 5 Conjugate P/PEG(2%)/TMZH(30%)

N-Hydroxysuccinimide (NHS) (1 mmol) and N,N′-dicyclohexylcarbodiimideDCC (1 mmol) dissolved in 2 ml of DMF were added consecutively to thesolution of 116 mg of PMLA (1 mmol with regard to malyl units) dissolvedin 1 ml of anhydrous acetone under vigorous stirring at room temperature(RT). The reaction mixture became turbid almost immediately uponaddition of the NHS/DCC mixture indicating the formation ofdicyclohexylurea. After stirring at RT for 3 h to complete theactivation of carboxyl groups, 0.02 mmol of mPEG₅₀₀₀-NH₂ (in 0.5 ml ofDMF, 2 Mol-% with regard to malyl units) was added followed by 0.02 mmolof triethylamine (TEA). After the reaction was completed according toTLC/ninhydrin test, the reaction mixture was filtered and most of thesolvent was removed by rotary evaporation. Next, 0.3 mmol of TMZH (15mg/ml in DMF, 30 Mol-% with regard to malyl units) was added drop-wiseat RT under stirring followed by 0.3 mmol of TEA. The reaction wascomplete within 2 h according to TLC (Rf=0.4 for TMZH; Rf=0 for thepolymer conjugate; chloroform:methanol 9:1; visualization under UV andby ninhydrin). Addition of 5-6 ml 100 mM sodium phosphate buffercontaining 150 mM NaCl (pH 6.0) to the reaction mixture was followed by30 min stirring at RT. After centrifugation at 1500×g for 10 min theclear supernatant was passed over a Sephadex column (PD-10, GEHealthcare, Piscataway, N.J., USA) pre-equilibrated with deionized (DI)water. The product containing fractions were collected and conjugateP/PEG(2%)/TMZH(30%) was obtained after freeze drying.

Example 6 Conjugate P/PEG(2%)/LOEt(40%)/TMZH(17%)

PMLA activation and conjugation of PEG followed the method described forconjugate P/PEG(2%)/TMZH(30%). A solution of LOEt hydrochloride (200 mMin DMF, 40 Mol-% with regard to malyl units) was added drop-wise at RTunder stirring followed by addition of 0.4 mmol of TEA. The reaction wascomplete after 2 h according to TLC (Rf=0 for the polymer conjugate,Rf=0.67 for LOEt; n-butanol:acetic acid:water 4:2:2) and visualizationof spots by ninhydrin. Next, 0.17 mmol of TMZH (15 mg/ml in DMF, 17Mol-% with regard to malyl units) was added drop-wise under stirring atRT followed by 0.17 mmol of TEA. After reaction completion in 2 h asjudged by TLC (Rf=0.4 for TMZH; Rf=0 for the polymer conjugate;chloroform:methanol 9:1), UV and ninhydrin test, conjugate was dissolvedin phosphate buffer, isolated as described for P/PEG(2%)/TMZH(30%), andfreeze dried. To isolate the intermediate product P/PEG(2%)LOEt(40%),the same method for isolation was used and the product was obtainedafter freeze drying.

Example 7 Synthesis of Conjugate P-LLL(40%)/TMZH(17%)

PMLA activated at carboxyl groups was prepared as described forconjugate P/PEG(2%)/TMZH(30%). A solution of LLL, 0.4 mmol, 50 mg/ml inDMF (40 Mol-% with regard to malyl units) and TFA (125 Mol-% with regardto LLL, to dissolve the tripeptide) was added at RT. TEA (0.4 mmol inDMF, 1:25 v/v) was then added slowly over 30 min. After 2-3 h thereaction was complete by TLC (Rf=0 for polymer conjugate; Rf=0.6 forLLL; n-butanol:acetic acid:water 4:2:2) and by ninhydrin test. ConjugateP/LLL(40%) was dissolved in phosphate buffer and isolated as describedfor conjugate P/PEG(2%)/TMZH(30%). In order to maximize TMZH loading, asecond round of carboxyl activation was performed: A solution of NHS(0.217 mmol) and of DCC (0.217 mmol) in 1 ml of DMF were addedconsecutively to the solution of 56 mg of P/LLL(40%) (0.217 mmol of freeacid groups) dissolved in 1 ml of anhydrous DMF under vigorous stirringat RT. After stirring for 3 h at RT, 0.037 mmol of TMZH (15 mg/ml inDMF, 17 mol % with regard to malyl units) was added drop-wise at RT,followed by 0.037 mmol of TEA. The reaction mixture was stirred at RTfor 3 h and the conjugate was isolated as described forP/PEG(2%)/TMZH(30%).

Example 8 Synthesis of P/PEG(2%)/LLL(40%)/TMZH(17%)/MEA(3%)

This conjugate was used for the conjugation of antibody. The conjugatenot containing 2-MEA was synthesized in the absence of this reagent.PMLA activated at carboxyl groups was prepared as described forconjugate P/PEG(2%)/TMZH(30%). A solution of LLL, 0.4 mmol, in DMF 50mg/ml (40 Mol-% with regard to malyl units) and TFA (125 Mol-% withregard to LLL) was added drop-wise to dissolve the tripeptide at RT. TEA0.4 mmol in DMF (1:25 v/v) was then added slowly over 30 min. Thereaction was complete after 2-3 h by TLC (Rf=0 for polymer conjugate;Rf=0.6 for LLL; n-butanol:acetic acid:water 4:2:2) and by ninhydrintest. Next, TMZH (15 mg/ml in DMF, 17 Mol-% or optionally 30 Mol-% withregard to malyl units) was added drop-wise under stirring at RT followedby equivalent amount of TEA. After reaction completion in 2-3 h, asjudged by TLC (Rf=0.4 for TMZH; Rf=0 for the polymer conjugate;chloroform:methanol 9:1), UV, and ninhydrin test, 0.05 mmol of 2-MEA inDMF (100 μl, 5 Mol-% with regard to malyl units) was added to thereaction mixture. After reaction completion in 30-40 mM (TLC andninhydrin test), conjugate was dissolved in phosphate buffer andisolated as described for conjugate P/PEG(2%)/TMZH(30%).

Example 9 Conjugate P/PEG(2%)/LLL(40%)/TMZH(17%)/HuTfR mAb(0.25%)

A solution of Anti-human TfR mAb (HuTfR)/PEG₃₅₀₀/maleimide (2 mg/ml)synthesized as described (28) and dissolved in 100 mM sodium phosphatebuffer containing 150 mM NaCl (pH 6.0) was added dropwise at roomtemperature to a solution of P/PEG(2%)/LOEt(40%)/TMZH(17%)/MEA(3%) at 2mg/ml in the same buffer. After stirring overnight at 4° C., remainingfree —SH groups were blocked by excess PDP (50 mg/ml in DMF) by stirringfor 30 mM at room temperature. The product was concentrated over acentrifuge membrane filter VIVASPIN 20, cutoff 30 kDa, 20 ml at 1500×g(Sartorius Stedim Biotech, Concord, Calif., USA), and the final volumewas adjusted to 2 ml before purification over Sephadex G-75 preequilibrated with buffer, sodium phosphate 100 mM, NaCl 150 mM, pH 6.8.Product containing fractions were isolated, combined and concentratedvia membrane filtration. Similar methods were used to synthesize otherantibody containing conjugates.

Example 10 Fluorescent Labeling of Conjugates

Alex680 dissolved in DMF at 1 mg/ml was added to the solution of desiredconjugates (2 mg/ml) in 100 mM sodium phosphate buffer with 150 mM NaCl,pH 5.5. The reaction mixture was stirred at RT for 1 h and passed overSephadex G-75 pre equilibrated with 100 mM sodium phosphate buffer, 150mM NaCl, pH 6.8. The product was concentrated via membrane filtration.For the antibody containing conjugates, Alex680 labeling was performedbefore blocking of excess free thiol groups by PDP.

Example 11 Calculation of Molecular Weights of Nanoconjugates

Molecular weights of nanoconjugates were calculated as shown forconjugate P/PEG(2%)/LLL(40%)/TMZH(17%) as an example: 100% malic acidresidues (FW 116)=862 monomers of PMLA (Mw=100 kDa). Mw fraction ofmalic acid with free —COOH (FW116) is 41%=353.4×116 Da: 41.0 kDa.Fraction conjugated malic acid (FW 99) is 59%=508.6×99 Da: 50.3 kDa.Fraction mPEG₅₀₀₀ (FW 5000) is 2%=17.2×5000 Da: 86.2 kDa. Fraction LLL(FW 357.5) is 40%=344.8×357.5 Da: 123.3 kDa. Fraction TMZH (FW 210.63)is 17%=146.5×210.63: 30.8 kDa. Total estimated average Mw of conjugateis 332 kDa.

Example 12 Hydrodynamic Diameter and Zeta Potential

Synthesized conjugates were characterized with respect to their size andζ potential using a particle and molecular size analyzer ZETASIZER NanoZS90 (Malvern Instruments, Malvern, UK). The size was calculated on thebasis of noninvasive back-scattering (NIBS) measurements using theStokes-Einstein equation, d(H)=kT/3πηD. d(H) is the hydrodynamicdiameter, D translational diffusion coefficient, k Boltzmann's constant,T absolute temperature, and η viscosity. The diameter that is measuredin DLS (Dynamic Light Scattering) refers to the particle diffusionwithin a fluid and is referred to as the hydrodynamic diametercorresponding to the diameter of a sphere that has the sametranslational diffusion coefficient as the particle. The ζ potential wascalculated from the electrophoretic mobility based on theHelmholtz-Smoluchowski formula, using electrophoresis M3-PALS (29, 30).All calculations were carried out by the ZETASIZER 6.0 software. For theparticle size measurements at 25° C., the solutions were prepared in PBSat a concentration of 2 mg/ml, filtered through a 0.2 1 μm poremembrane. For the measurement of the ζ potential, the concentration ofthe sample dissolved in water containing 10 mM NaCl was 2 mg/ml, and thevoltage applied was 150 V. All the conjugate solutions were preparedimmediately before analysis at 25° C. Data represent the mean±standarddeviation obtained for three measurements.

Example 13 Liposome Leakage Assay

Fluorescent assay for calcein release from loadedphosphatidylcholine/cholesterol liposomes (31) purified over theSEPHADEX G-50 gel was used to determine leakage activity of synthesizedpolymer conjugates. To assess leakage at different pH values,nanoconjugates were serially diluted in 50.mu.l buffer containingappropriate mixtures of 137 mM HEPES, pH 7.4 and 137 mM citrate, pH 5.0.Triplicate samples were mixed with 50.mu.l liposome suspensions in 5 mMHEPES buffer, 150 mM NaCl, pH 7.4 (final lipid concentration 160.mu.M).After 1 h at RT, fluorescence was read by an ELISA reader at 485 nmexcitation and 535 nm emission wavelengths. The detergent TRITON X-100,0.25% (v/v), was used as a reference for 100% leakage.

Example 14 Conjugate Degradation Study

The degradation of nanoconjugates in human plasma was carried out at 37°C. with a polymer concentration of 1 mg/ml. The sample vials were sealedto avoid evaporation and stored at 37° C. in an incubator. For theisolation from the plasma, aliquots of 1 ml were extracted with 5 ml ofchloroform/ethyl acetate (1:1 v/v). The copolyester contained in theorganic phase was dried and re-dissolved in PBS buffer. Size reductiondue to degradation was followed by measurement of the hydrodynamicdiameter in a particle and molecular size analyzer ZETASIZER or of themolecular weight by SEC-HPLC. Sample preparation with the polymers ofknown M_(w) was used to verify that the isolation method had no effecton molecular weights. Degradation in PBS (pH 7.4) was followed at aconcentration of 1 mg/ml for each copolymer. The change in size of thenanoconjugate either by SEC-HPLC or hydrodynamic diameter (a particleand molecular size analyzer ZETASIZER) was measured as a function ofdegradation time. Molecular weights M_(w)(t) and hydrodynamic diameter(t) were plotted as a function of degradation time with reference ofthese properties at zero incubation time.

Example 15 Cell Viability

Primary glioma cell lines U87MG and T98G, and invasive breast carcinomacell lines MDA-MB-231 and MDA-MB-468 were obtained from American TypeCulture Collection (ATCC, Manassas, Va., USA) USA. U87MG and T98G cellswere cultured in MEM supplemented with 10% fetal bovine serum, 1% MEMNEAA, 1 mM sodium pyruvate and 2 mM L-glutamine. For MDA-MB-231 andMDA-MB-468, Leibovitz's L-15 medium with 10% fetal bovine serum wasused. Cells were seeded at 10³ per well (0.1 ml) in 96-wellflat-bottomed plates and incubated overnight at 37° C. in humidatmosphere with 5% CO₂ (MDA-MB-231 and MDA-MB-468 were incubated withoutCO₂). After exposure to synthesized conjugates for 24 h, medium wasreplaced every 48 h. Cell viability was measured on day 5 for T98G andday 7 for the rest of the cell lines using the CELLTITER 96 Aqueous OneSolution Cell Proliferation Assay kit (Cat. No. PR-G3580; Promega,Madison, Wis., USA). Yellow[3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl-)-2H-tetrazolium,inner salt] (MTS) is bioreduced by cells into formazan that is solublein the tissue culture medium. The absorbance reading at 490 nm from the96-well plates is directly proportional to the number of living cells(32). The viability of the untreated cells was taken as 100%. Theresults shown are the mean±standard deviation of three independentmeasurements. Data were analyzed by statistical software GRAPHPAD PRISM3.0.

Example 16 Confocal Microscopy

1×10⁵ U87MG cells were seeded on Lab-Tek chamber slides (Thermo FisherScientific, Rochester, N.Y., USA) for 24 h. The cells were washed oncewith serum-free media and incubated with Alex680 fluorescently labeledconjugates in 500 μl serum-free media at 50 μg/ml forP/PEG(2%)/LLL(40%)TMZH(17%)/Alex680(1%) and at 100 μg/ml forP/PEG(2%)/LLL(40%)TMZH(17%)/HuTfR mAb(0.25%)/Alex680(1%). After 1 hincubation at 37° C. in humid atmosphere with 5% CO₂, the cells werewashed three times with PBS and finally incubated in fresh media withserum for live confocal imaging in a TCS SP spectral scanner (LeicaMicrosystems, Mannheim, Germany) Image stacks of 246 by 246 μm in sizeand 7.5 μm in depth of live U87MG glioma cells were acquired with a HCXPL APO CS 63.0×1.20 lens. Live cells were placed on chamber slidesmaintaining 37° C. temperature, humidity and 5% CO₂ by a separate lensand chamber heating system. The spectral settings were optimized forAlex680, excitation 670 nm and emission 685-750 nm. The images wereprocessed by ImageJ 1.41o software from NIH.

Example 17 Nanoconjugate Syntheses

The multi component drug delivery system schematically presented in FIG.1 was synthesized with PMLA as the platform and prodrug TMZ in itshydrazide form, H₂N-Leu-Leu-LeuOH (LLL) or NH₂-LeuOEt (LOEt) fordisruption of endosomal membrane, antibodies for targeting, and PEGagainst resorption and enzyme degradation. The first part of theconjugation included the chemical activation of the PMLA pendantcarboxyl groups forming the NHS-ester and subsequently the nucleophilicreplacement by forming stable amide bonds. Conjugation of antibodies viathioether bond formation followed in the second part. Because of thePMLA chain length inhomogeneity, an excess of mAb was chosen in order toincrease the likelihood that at least one molecule was conjugated witheach polymer chain. The amount of 40% of carboxyl groups conjugated withLLL for most efficient membrane disruption activity limited the amountof TMZH conjugation to 17%. In order to increase the amount of TMZHloading, carboxyl activation was repeated after conjugation with LLLbefore conjugation with TMZH. Obtained nanoconjugates of higher than 17%TMZH were, however, found insoluble in aqueous buffer. Care was taken toavoid neutral or alkaline conditions as well as elevated temperatures(>22° C.) in order to keep hydrolytic degradation of TMZ at a minimum.Freeze-dried intermediates and products could be stored at −20° C. forseveral months without measurable loss in chemical or physiologicalreactivity.

Example 18 Purity and Physicochemical Characterization

Products were highly soluble in aqueous solution without formingprecipitates as judged by SEC-HPLC and a particle and molecular sizeanalyzer ZETASIZER. Preparations were tested for small molecular weightimpurities by TLC and ninhydrin reaction. On this basis of SEC-HPLCresults (using multiple wavelengths for scanning) and hydrodynamicdiameter scanning, the investigated conjugates were pure, i.e.consisting of single compounds. The amount of TMZH in the conjugatepreparations was validated by UV absorbance at 328 nm using knownamounts of free TMZH as standards. By ¹H NMR analysis using integrationof methyl group signals of TMZH and of PMLA protons the TMZH contentswere analyzed. TMZ contents by NMR and UV measurement were the samewithin 3% deviation measured for conjugate P/PEG(2%)/TMZH(30%).Conjugates had characteristic values of hydrodynamic diameters and zetapotentials (Table I). Free PMLA and P/LLL(40%)/TMZH(17%) had thesmallest hydrodynamic diameter, whereas additionally conjugated PEG₅₀₀₀increased the diameter by about 2 nm and mAb, by about 8 nm. The valueof ζ potential can be used to differentiate between PMLA, −22.9 mV, andnanoconjugates with neutral ligands like TMZH, LOEt, for example −7 mVfor P/PEG(2%)/LOEt(40%)/TMZH(17%), and conjugates with charged ligandslike LLL (instead of LOEt), for example −11.5 mV forP/PEG(2%)/LLL(40%)/TMZH(17%) (Table 1). Conjugates were alsodistinguished by other properties, e.g., by their capability forliposome leakage. As shown in FIG. 2, the conjugateP/PEG(2%)LLL(40%)/TMZH(17%) was pH-sensitive, whereas the conjugateP/LLL(40%)/TMZH(17%) was not. Another property was the effect on U87MGand MDA-MB-468 cell viability. It was more affected by the conjugateP/LLL(40%)/TMZH(17%) (FIG. 4) than by P/PEG(2%)LLL(40%)/TMZH(17%) (FIG.6).

Example 19 Half-Life of Free and Conjugated TMZH

TMZ is a prodrug and undergoes spontaneous conversion to the activealkylating agent at neutral or alkaline pH. Half-lives were measured atphysiological pH 7.4 in PBS and summarized in Table I. The decompositionof free and conjugated TMZH by hydrolytic ring opening (Chart 1) was afirst order reaction for free TMZ or TMZH and conjugated TMZH (data notshown). For TMZ, the half-life was 1.80±0.1 h and for TMZH, 1.98±0.1 h.Half-life was significantly enhanced, about 3-4 times, after conjugationwith the polymer. For example, TMZ had a half life of 7.34±0.2 h forconjugate P/LLL(40%)/TMZH(17%) and 7.10±0.2 h for P/PEG(2%)/TMZH(30%)(Table I). Similar data have been reported for TMZ conjugated with smallcarbon chains (6). No detectable decomposition was observed during 24 hat pH 5.0 at RT.

Example 20 Stability and Degradation Measured by Size

Degradation of synthesized nanoconjugates was measured by SEC-HPLC and aparticle and molecular size analyzer ZETASIZER in terms of molecularweight and hydrodynamic diameter respectively (data not shown). In PBSat 4° C., all synthesized nanoconjugates were stable maintaining over85% of original M_(w)/size for more than 72 h. However, at temperatures25° C. and especially at 37° C., substantial degradation was observedand M_(w)/size was reduced to 50% after 24-72 h in PBS. In human plasmaat 37° C., conjugates degraded more rapidly compared with degradation inPBS and M_(w)/size was reduced by 50% after 12-36 h. As an example,degradation of conjugate P-LLL(40%)/TMZH(17%) is shown in FIG. 3.

Example 21 Membrane Destabilization

As an uncharged prodrug, TMZ can passively permeate the cells, where itis ultimately activated to the nucleic acid methylating methyldiazoniumcation (33). Targeting of glioma cells by conjugated mAb would involvebinding of the nanoconjugate delivery vehicle to overexpressed TfR andsubsequent internalization into the endosomal system. In order todeliver the desired drug into the cytoplasm, disruption of the endosomalmembrane would be essential. By systematic structure variation usingPMLA as nanoplatform and membranes of artificial liposomes we have foundLOEt and LLL substituting 40% of pendant PMLA carboxyates of theplatform to be excellent candidates for endosomal membrane disruption(FIG. 2). Whereas the LLL unit was active only at pH 6-5.0 (FIG. 2 a),resembling pH of late endosomes and lysosomes, the membrane disruptionactivity of the LOEt unit was pH-independent. The pH-dependence for LLLwas referred to the ionization of the tripeptide carboxyl group. ThepK_(a) that governs ionization was shifted by conjugation with PMLAtowards the neutral pH region due to the hydrophobic shielding by themultiple conjugated leucine side chains (Ding et al. “Poly(β-L-malicacid) with pendent leu-leu-leu-OH for endosome-routed cytoplasmicdelivery”. 14^(th) International Symposium on Recent Advances in DrugDelivery Systems, Salt Lake City, 2009, Abstract #91). FIG. 2 showsexamples of liposome leakage caused by membrane disruption in theabsence and presence of TMZH. LOEt was the more effective membranedisrupting agent (FIG. 2 a). The loading by TMZH slightly increased theliposome leakage activity by LOEt and LLL units, but did not abolish thepH dependence for conjugate P/PEG(2%)LLL(40%)/TMZH(17%) (FIG. 2 b). WhenTMZH was conjugated as in P/LLL(40%)/TMZH(17%), the leakage activity wasimproved and the pH-sensitivity disappeared (FIG. 2 b). Most likely,this change was attributed to conjugation of TMZH with LLL-COOH residuesthus eliminating the carboxylates that before gave rise to the observedpH dependence.

Example 22 Cell Viability Study

Effects of the nanoconjugates on cell viability were measured in orderto investigate the influence of the delivery system on the TMZH prodrugactivity and to test for cytotoxic activities of the delivery systemitself in the absence of the prodrug. Results were compared with thosefor free TMZ and TMZH in a dose-dependent manner. P/PEG(2%)/TMZH(30%)had no significant effect on viability compared with free TMZ in thecase of human glioma cell line U87MG (FIG. 4 a), and it was ineffectiveon T98G, MDA-MB-231 and MDA-MB-468 cell lines (FIG. 4 b-d). Conjugationof membrane disruption unit had pronounced effects on cell viability.Introduction of LOEt as a membrane disruption unit seemed to decreasecell viability significantly (FIG. 5); however, the decrease wasapparently due to the nanoconjugate P/PEG(2%)/LOEt(40%) carrier itselfand not by conjugated TMZH. As LOEt negatively affected cell viabilityin the observed concentration range, conjugates with this endosomalescape unit were not further considered. Importantly, introduction ofLLL in the conjugate P/LLL(40%)/TMZH(17%) significantly decreased cellviability of all four cell cultures, gliomas U87MG and T98G, and breastcancer cell lines MDA-MB-231 and MDA-MB-468. In the same assay, free TMZwas inactive in all lines except U87MG. Conjugate P/LLL(40%) as acontrol had little or no effect on cell viability due to the absence ofthe prodrug (FIG. 4) and this was not changed by the addition ofPEG₅₀₀₀. The effect of coupling anti-TfR mAb to the nanoconjugate isshown in FIG. 6 a. Whereas free TMZ had a stronger effect on U87MG cellsthan the nanoconjugates, these showed an increasing potency in the orderP/PEG(2%)/LLL(40%)/TMZH(17%)/IgG(0.25%)<P/PEG(2%)/LLL(40%)/TMZH(17%)<P/PEG(2%)/LLL(40%)/TMZH(17%)/HuTfRmAb(0.25%)<TMZ. In contrast, with the cell line MDA-MB-468, free TMZ wasineffective at all concentrations below 130 μM, whereas conjugatesP/PEG(2%)/LLL(40%)/TMZH(17%)/IgG(0.25%), P/PEG(2%)/LLL(40%)/TMZH(17%),P/PEG(2%)/LLL(40%)/TMZH(17%)/HuTfR mAb(0.25%) showed significantreduction in viability and were almost equally effective.

Example 23 Confocal Microscopy

The uptake of nanoconjugates was imaged by confocal microscopy followingthe appearance of fluorescence inside live human glioma U87MG cells(FIG. 7). Uptake into vesicles was observed for both conjugatesP/PEG(2%)/LLL(40%)/TMZH(17%) and P/PEG(2%)/LLL(40%)/TMZH(17%)/HuTfRmAb(0.25%) labeled with Alex680. At a fixed instrument setting, theintensity and the number of vesicles was higher for the activelytargeting conjugate with TfR mAb than for the conjugate lacking theantibody. It can be concluded that the nanodrugs were internalized mostlikely by receptor-mediated endocytosis and possibly also by pinocytoticpathways.

Example 24 Discussion

Orally applied TMZ to treat human gliomas has the potency to bedistributed all over the entire organism. After penetration of thelipophilic prodrug through membranes into the cytoplasm of recipientcells it will be activated by the hydrolytic mechanism described herein.The active drug is then ready to methylate proteins and especially DNA,guanine at N7 position, followed by methylation of adenine at the O3position and of guanine at the O6 position (33). Failure of repair willdrive these cells into apoptosis. Hydrolytic activation of the prodrugat sites other than the cytoplasm is inefficient due to the fact thatthe cationic methyl diazonium like any other charged molecule cannotpassively penetrate membranes.

The inventors have succeeded to conjugate TMZ via the hydrazide bond tothe highly negatively charged PMLA that renders the prodrug no longerdiffusible through membranes. As a consequence, the active methyldiazonium cation can only be generated from the nanodrug. Free passivediffusion of the PMLA conjugate into recipient cells is highly unlikelybecause of its high negative charge, and generation of active drugoutside the cytoplasm would not be effective due to its own intrinsiccharge. Therefore, the nanodrug can only give rise to nucleic acidmethylation if it is internalized into the cytoplasm of recipient cells.The results in FIG. 7 show that drug uptake follows most likelyreceptor-mediated endocytosis and possibly pinocytotic pathways of theconjugates P/PEG(2%)/LLL(40%)/TMZH(17%)/HuTfR mAb(0.25%) andP/PEG(2%)/LLL(40%)/TMZH(17%) that were labeled with Alex680. Withoutexiting from the endosome into the cytoplasm, drug activation would bestill ineffective due to the vesicle membrane barrier, explaining whyconjugate P/PEG(2%)/TMZH(30%) without any endosome disruption unit didnot affect cell viability (FIG. 4). Moreover, maturing endosomes undergoacidification rendering drug activation unlikely, because this requiresneutral or higher pH. If the nanodrug carries the membrane disruptingLLL device as in the case of the above conjugates, it could enter thecytoplasm, and there, by virtue of physiological pH, the prodrug couldbe converted into its active form and methylate DNA.

To satisfy the above mechanism, the inventors synthesized the nanodrugcarrying targeting TfR antibodies, endosome escape unit, and theprodrug. The results in FIGS. 4 and 6 show the delivery and prodrugactivation to follow the anticipated mechanism. The effect of thetargeting HuTfR mAb was observed in the case of human glioma U87MGcells. A significant reduction of viability is seen in the presence ofthe endosome escape unit LLL for all cell lines shown in FIGS. 4 and 6.This in agreement with the stringent requirement for endosome escape inthe prodrug delivery mechanism.

Whereas glioma U87MG cells responded to treatment with free TMZ, cellviability of glioma T98G and breast cancer MDA-MB-231 and MDA-MB-468cells did not change. These cell lines are known to be TMZ resistant(32-34). In the case of T98G cells, resistance has been referred tooverproduction of O6-methyl guanine methyltransferase (MGMT) (32), thatof MDA-MB-231 cells has been associated with unbalanced expression ofDNA glycosylase and DNA polymerase expression (34), and the mechanism ofresistance is not known for MDA-MB-468 cells. If indeed the lack ofresponse to free TMZ for T98G, MDA-MB-231 and MDA-MB-468 in FIG. 4referred to TMZ resistance, the observed significant decrease of cellviability (FIGS. 4 and 6) showed that the nanoconjugatesP/PEG(2%)/LLL(40%)/TMZH(17%), P/LLL(40%)/TMZH(17%)/HuTfR mAb(0.25%) andP/LLL(40%)/TMZH(17%)/IgG(0.25%) had the ability to overcome theresistance. On the basis of their unique results, conjugatesP/PEG(2%)/LLL(40%)/TMZH(17%) and P/LLL(40%)/TMZH(17%)/HuTfR mAb(0.25%)were designed as lead compounds with potential for treatment of glialtumors in vivo.

The drug delivery system offers a biodegradable, non-toxic, andnon-immunogenic scaffold obtained from a biological source, thus openingan avenue for drug delivery without the danger of liver storage disease.Conjugation of TMZH to this platform has been challenging because of thesensitivity of the prodrug to neutral and alkaline pH. Nonetheless,syntheses of TMZ nanodrugs have been worked out to be readily achievableand highly reproducible. The solution properties such as solubility andabsence of aggregation, size in the nanometer range, and slightlynegative zeta potential are favorable for drug delivery (35, 36). One ofthe lead conjugates contains PEG₅₀₀₀, which minimizes enzymatic nanodrugdegradation and clearance by the reticulo-endothelial system (37). Thenanodrugs are stable in human plasma over several hours, and the rangeof half-life for active drug formation has increased several-fold overthat of free TMZ by conjugation to the PMLA platform. The increasedhalf-life of conjugated TMZ favors an efficient delivery of functionalprodrug in vivo. On the basis of the data, the following in vivoscenario is likely: After I.V. application, the nanodrug will beaccumulated in the interstitial space of malignant glioma by EPR effect(19) and/or active mAb targeting of overexpressed TfR on vascularendothelium next to the tumor (21). From the interstitium, the nanodrugwill enter the endosomal system of tumor cells and become activated inthe cytoplasm after endosomal escape. Accumulation in the tumor by EPReffect and especially, active mAb targeting provides efficiency of tumortreatment with minimal side effects for healthy tissue.

Example 25

TABLE 1 Physicochemical properties of the conjugates and half-lives ofTMZ Hydrodynamic Zeta Half-life diameter potential of TMZ Conjugates(nm)^(a) (mV)^(b) (h)^(c) TMZ n.d. n.d.  1.80 (±0.1)^(d) TMZH n.d. n.d.1.98 (±0.1) PMLA 6.6 (±0.1) 22.9 (±1.7) n.d. P/PEG(2%)/TMZH(30%)^(e) 7.8(±0.4) 16.1 (±1.2) 7.10 (±0.2) P/PEG(2%)/LOEt(40%)/ 8.5 (±0.4) −6.7(±0.2) 4.92 (±0.3) TMZH(17%) P/PEG(2%)/LLL(40%)/ 6.9 (±1.3) 11.5 (±1.8)6.25 (±0.2) TMZH(17%) P/LLL(40%)/TMZH(17%) 6.5 (±0.2) 17.7 (±2.1) 7.34(±0.2) P/PEG(2%)/LLL(40%)/ 14.8 (±2.1)  −6.3 (±1.7) n.d.TMZH(17%))/HuTfR mAb(0.25%) ^(a)Hydrodynamic diameter at 25° C. measuredin PBS at a concentration of 2 mg/ml; ^(b)ζ potential at 25° C. inaqueous solution of 10 mM NaCl at 150 V; ^(c)half-life measured atphysiological pH in PBS at 37° C.; ^(d)Mean values and S.D. for threeindependent measurements; ^(e)percentage refers to total number (100%)of pendant carboxyl groups in unsubstituted PMLA; n.d., not done.

Example 26 Conclusions

For the purpose of targeting TMZ to human glioma, TMZH was conjugated toPMLA platform, which was equipped with anti-human TfR antibodies fortumor cell targeting by receptor mediated endocytosis; and pH-dependentLLL for endosome escape. The lead compoundsP/PEG(2%)/LLL(40%)/TMZH(17%)/HuTfR mAb(0.25%) and P/LLL(40%)/TMZH(17%)showed significant reduction in tumor cell viability of both humanglioma and human breast cancer cell lines. Cell viability wassignificantly reduced in cases of TMZ-resistant cell lines where freeTMZ had no effect.

Example 27 Efficacy of Delivery System In Vivo

After numerous in vitro screening, it was important to investigate theefficacy of delivery system in vivo. To prove the concept, subcutaneousmodel was used using human glioma U87MG cell line. 3×10⁶ cells wereinoculated in nude mice and tumors were formed. ConjugateP/PEG(2%)/LLL(40%)/TMZ(15%) was chosen for the in vivo study and wassynthesized following a similar procedure described for conjugateP/PEG(2%)/LOEt(40%)/TMZH(17%).

After inoculation of human glioma cells in nude mice, all the animalswere randomized as the average tumor volume reached about 125 mm³ (day28 after inoculation). Animals were divided in two different groups asshown in Table 2. Nanoconjugates are highly soluble in aqueous solutionsand were dissolved in PBS prior to the administration. Drug wasadministered intravenously (I.V.) for five consecutive days at atemozolomide concentration of 4 mg/kg. Tumor volume was measured 3 timesa week and all the animals were euthanatized on day 37.

TABLE 2 Treatment plan for tumor bearing mice with temozolomidenanoconjugate. Group 1 Group 2 n = 4 n = 4 PBS P-PEG(2%)LLL(40%)/TMZ(15%) IV for 5 days 4 mg/kg (TMZ concentration) 65 mg/kg (nanoconjugateconcentration) IV for 5 days

Treatment of animals with P/PEG(2%)/LLL(40)/TMZ(15%) {With 4 mg/kg ofTMZ concentration} showed significant tumor growth inhibition comparedwith PBS treated animals. (p=0.0024, calculated from tumor growth rateas shown herein in FIG. 12). Temozolomide conjugateP/PEG(2%)/LLL(40)/TMZ(15%) at lower concentration (1 mg/kg of TMZ) didnot achieve the desired effect. FIG. 13 illustrates the total tumorvolume of different treatment groups.

Temozolomide nanoconjugate synthesized using polymalic acid as aplatform significantly inhibited the tumor growth and proved itsefficacy in vivo. Even without any active targeting, the nanoconjugatewas effective.

Example 28 Temozolomide (TMZ) Dosage

FDA-approved dosage to treat patients in clinic using oraladministration:

Newly Diagnosed High Grade Glioma:

-   -   75 mg/m² (corresponds to 2.3 mg/kg) daily p.o. for 42 days        combined with focal radiotherapy followed by maintenance        temozolomide for six cycles.        Maintenance Phase:    -   Cycle 1: 150 mg/m² (corresponds to 4.6 mg/kg) p.o. daily        followed by 23 days without treatment.    -   Cycle 2 to 6: 200 mg/m² (corresponds to 6.15 mg/kg) p.o. daily        followed by 23 days without treatment if toxicity does not        occur.

In conjunction with various drug delivery systems described herein, TMZcan be administered via I.V. injection. As described herein, theinventors used mouse xenograft (U87MG, human glioma): 4 mg/kgintravenous injections for 5 consecutive days. As a result, the drug isless toxic because the direct tumor delivery and drug concentration inthe tumor site is higher than after oral drug is administrated. TMZcovalently attached on polymer overcomes drug resistance.

Various embodiments of the invention are described above in the DetailedDescription. While these descriptions directly describe the aboveembodiments, it is understood that those skilled in the art may conceivemodifications and/or variations to the specific embodiments shown anddescribed herein. Any such modifications or variations that fall withinthe purview of this description are intended to be included therein aswell. Unless specifically noted, it is the intention of the inventorthat the words and phrases in the specification and claims be given theordinary and accustomed meanings to those of ordinary skill in theapplicable art(s).

The foregoing description of various embodiments of the invention knownto the applicant at this time of filing the application has beenpresented and is intended for the purposes of illustration anddescription. The present description is not intended to be exhaustivenor limit the invention to the precise form disclosed and manymodifications and variations are possible in the light of the aboveteachings. The embodiments described serve to explain the principles ofthe invention and its practical application and to enable others skilledin the art to utilize the invention in various embodiments and withvarious modifications as are suited to the particular use contemplated.Therefore, it is intended that the invention not be limited to theparticular embodiments disclosed for carrying out the invention.

While particular embodiments of the present invention have been shownand described, it will be obvious to those skilled in the art that,based upon the teachings herein, changes and modifications may be madewithout departing from this invention and its broader aspects and,therefore, the appended claims are to encompass within their scope allsuch changes and modifications as are within the true spirit and scopeof this invention. Furthermore, it is to be understood that theinvention is solely defined by the appended claims. It will beunderstood by those within the art that, in general, terms used herein,and especially in the appended claims (e.g., bodies of the appendedclaims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to inventions containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should typically be interpreted to mean “atleast one” or “one or more”); the same holds true for the use ofdefinite articles used to introduce claim recitations. In addition, evenif a specific number of an introduced claim recitation is explicitlyrecited, those skilled in the art will recognize that such recitationshould typically be interpreted to mean at least the recited number(e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations).

Accordingly, the invention is not limited except as by the appendedclaims.

REFERENCES

-   1. D. N. Louis, H. Ohgaki, O. D. Wiestler, W. K. Cavenee, P. C.    Burger, A. Jouvet, B. W. Scheithauer, and P. Kleihues. The 2007 WHO    classification of tumours of the central nervous system. Acta    Neuropathol. 114:97-109 (2007).-   2. 2009 CBTRUS Statistical Report: Primary Brain and Central Nervous    System Tumors Diagnosed in the United States in 2004-2005.    http://www.cbtrus.org/reports/2009-NPCR-04-05/CBTRUS-NPCR2004-2005-Report-.pdf    (accessed Nov. 17, 2009).-   3. A. R. Asthagiri, N. Pouratian, J. Sherman, G. Ahmed, and M. E.    Shaffrey. Advances in brain tumor surgery. Neurol Clin. 25:975-1003    (2007).-   4. W. Stummer, U. Pichlmeier, T. Meinel, O. D. Wiestler, F. Zanella,    and H. J. Reulen. Fluorescence-guided surgery with 5-aminolevulinic    acid for resection of malignant glioma: a randomised controlled    multicentre phase III trial. Lancet Oncol. 7:392-401 (2006).-   5. M. Lacroix, D. Abi-Said, D. R. Fourney, Z. L. Gokaslan, W.    Shi, F. DeMonte, F. F. Lang, I. E. McCutcheon, S. J. Hassenbusch, E.    Holland, K. Hess, C. Michael, D. Miller, and R. Sawaya. A    multivariate analysis of 416 patients with glioblastoma multiforme:    prognosis, extent of resection, and survival. J. Neurosurg.    95:190-198 (2001).-   6. J. Arrowsmith, S. A. Jennings, D. A. Langnel, R. T. Wheelhouse,    and M. F. Stevens. Antitumour imidazotetrazines. Part 39 synthesis    of bis(imidazotetrazine)s with saturated spacer groups. J Chem Soc    Perkin Trans 1. 24:4432-4438 (2000).-   7. R. Stupp, W. P. Mason, M. J. van den Bent, M. Weller, B.    Fisher, M. J. Taphoorn, K. Belanger, A. A. Brandes, C. Marosi, U.    Bogdahn, J. Curschmann, R. C. Janzer, S. K. Ludwin, T. Gorlia, A.    Allgeier, D. Lacombe, J. G. Cairncross, E. Eisenhauer, and R. O.    Mirimanoff. Radiotherapy plus concomitant and adjuvant temozolomide    for glioblastoma. N Engl J. Med. 352:987-996 (2005).-   8. N. Auger, J. Thillet, K. Wanherdrick, A. Idbaih, M. E.    Legrier, B. Dutrillaux, M. Sanson, and M. F. Poupon. Genetic    alterations associated with acquired temozolomide resistance in    SNB-19, a human glioma cell line. Mol Cancer Ther. 5:2182-2192    (2006).-   9. C. C. Chen, K. T. Kahle, K. Ng, M. Nitta, and A. D. Andrea. Of    escherichia coli and man: understanding glioma resistance to    temozolomide therapy. In E. G. Meir (eds.), CNS Cancer, Humana    Press, Atlanta, 2009, pp 679-711.-   10. G. J. Kitange, B. L. Carlson, M. A. Schroeder, P. T.    Grogan, J. D. Lamont, P. A. Decker, W. Wu, C. D. James, and J. N.    Sarkaria. Induction of MGMT expression is associated with    temozolomide resistance in glioblastoma xenografts. Neuro Oncol.    11:281-291 (2009).-   11. R. Satchi-Fainaro, M. Puder, J. W. Davies, H. T. Tran, D. A.    Sampson, A. K. Greene, G. Corfas, and J. Folkman. Targeting    angiogenesis with a conjugate of HPMA copolymer and TNP-470. Nat.    Med. 10:255-261 (2004).-   12. R. Duncan. The dawning era of polymer therapeutics. Nat Rev Drug    Discov. 2:347-360 (2003).-   13. S. V. Vinogradov, E. V. Batrakova, S. Li, and A. V. Kabanov.    Mixed polymer micelles of amphiphilic and cationic copolymers for    delivery of antisense oligonucleotides. J Drug Target. 12:517-526    (2004).-   14. A. V. Kabanov, E. V. Batrakova, S. Sriadibhatla, Z. Yang, D. L.    Kelly, and V. Y. Alakov. Polymer genomics: shifting the gene and    drug delivery paradigms. J Control Release. 101:259-271 (2005).-   15. D. Peer, J. M. Karp, S. Hong, O. C. Farokhzad, R. Margalit,    and R. Langer. Nanocarriers as an emerging platform for cancer    therapy. Nat. Nanotechnol. 2:751-760 (2007).-   16. M. Ferrari. Cancer nanotechnology: opportunities and challenges.    Nat Rev Cancer. 5:161-171 (2005).-   17. A. Nori, and J. Kopecek. Intracellular targeting of    polymer-bound drugs for cancer chemotherapy. Adv Drug Deliv Rev.    57:609-636 (2005).-   18. R. Duncan, M. J. Vicent, F. Greco, and R. I. Nicholson.    Polymer-drug conjugates: towards a novel approach for the treatment    of endrocine-related cancer. Endocr Relat Cancer. 12:S189-S199    (2005).-   19. H. Maeda, J. Fang, T. Inutsuka, and Y. Kitamoto. Vascular    permeability enhancement in solid tumor: various factors, mechanisms    involved and its implications. Int Immunopharmacol. 3:319-328    (2003).-   20. M. Fujita, B. S. Lee, N. M. Khazenzon, M. L. Penichet, K. A.    Wawrowsky, R. Patil, H. Ding, E. Holler, K. L. Black, and J. Y.    Ljubimova. Brain tumor tandem targeting using a combination of    monoclonal antibodies attached to biopoly(b-L-malic acid). J Control    Release. 122:356-363 (2007).-   21. B. S. Lee, M. Fujita, N. M. Khazenzon, K. A. Wawrowsky, S.    Wachsmann-Hogiu, D. L. Farkas, K. L. Black, J. Y. Ljubimova, and E.    Holler. Polycefin, a new prototype of a multifunctional    nanoconjugate based on poly(b-L-malic acid) for drug delivery.    Bioconjug Chem. 17:317-326 (2006).-   22. E. Segal, and R. Satchi-Fainaro. Design and development of    polymer conjugates as anti-angiogenic agents. Adv Drug Deliv Rev.    61:1159-1176 (2009).-   23. S. Brem, B. Tyler, K. Li, G. Pradilla, F. Legnani, J. Caplan,    and H. Brem. Local delivery of temozolomide by biodegradable    polymers is superior to oral administration in a rodent glioma    model. Cancer Chemother Pharmacol. 60:643-650 (2007).-   24. U. Akbar, T. Jones, J. Winestone, M. Michael, A. Shukla, Y. Sun,    and C. Duntsch. Delivery of temozolomide to the tumor bed via    biodegradable gel matrices in a novel model of intracranial glioma    with resection. J Neurooncol. 94:203-212 (2009).-   25. L. X. Zhao, J. L. Wang, X. P. Dai, Y. F. Wang, and Z. Z. Ji.    Synthesis and antitumour activities of 3-substituted    4-oxo-3H-imidazo[5,1-d][1,2,3,5]tetrazine-8-carboxylic acids and    their derivatives. Chin J Med. Chem. 11:263-269 (2001).-   26. E. Holler, Poly(malic acid) from natural sources. In N. P.    Cheremisinoff (eds.), Handbook of Engineering Polymeric Materials,    Marcel Dekker, New York, 1997, pp. 93-103.-   27. J. Carlsson, H. Drevin, and R. Axen. Protein thiolation and    reversible protein-protein conjugation. N-Succinimidyl    3-(2-pyridyldithio)propionate, a new heterobifunctional reagent.    Biochem J. 173:723-737 (1978).-   28. J. Y. Ljubimova, M. Fujita, A. V. Ljubimov, V. P.    Torchilin, K. L. Black, and E. Holler. Poly(malic acid)    nanoconjugates containing various antibodies and oligonucleotides    for multitargeting drug delivery. Nanomedicine. 3:247-265 (2008).-   29. I. O. f. S. (ISO). Methods for Determination of Particle Size    Distribution Part 8: Photon Correlation Spectroscopy, International    Standard ISO 13321, 1996.-   30. P. C. Hiemenz, Light scattering by polymer solutions, In P. C.    Hiemenz (eds.), Polymer Chemistry: The Basic Concepts, Marcel    Decker, New York, 1984, pp. 659-661.-   31. F. N. Fu, and B. R. Singh. Calcein permeability of liposomes    mediated by type A botulinum neurotoxin and its light and heavy    chains. J Protein Chem. 18:701-707 (1999).-   32. T. J. Mosmann. Rapid colorimetric assays for cellular growth and    survival: application to proliferation and cytotoxicity assays.    Immunol Methods. 65:55-63 (1983).-   33. H. S. Friedman, T. Kerby, and H. Calvert. Temozolomide and    treatment of malignant glioma. Clin Cancer Res. 6:2585-2597 (2000).-   34. R. N. Trivedi, X. H. Wang, E. Jelezcova, E. M. Goellner, J. B.    Tang, and R. W. Sobol. Human methyl purine DNA glycosylase and DNA    polymerase b expression collectively predict sensitivity to    temozolomide. Mol. Pharmacol. 74:505-516 (2008).-   35. A. E. Nel, L. Madler, D. Velegol, T. Xia, E. M. Hoek, P.    Somasundaran, F. Klaessig, V. Castranova, and M. Thompson.    Understanding biophysicochemical interactions at the nano-bio    interface. Nat. Mater. 8:543-557 (2009).-   36. M. R. Lorenz, V. Holzapfel, A. Musyanovych, K. Nothelfer, P.    Walther, H. Frank, K. Landfester, H. Schrezenmeier, and V.    Mailander. Uptake of functionalized, fluorescent-labeled polymeric    particles in different cell lines and stem cells. Biomaterials.    27:2820-2828 (2006).-   37. D. E. Owens, and N. A. Peppas. Opsonization, biodistribution,    and pharmacokinetics of polymeric nanoparticles. Int J. Pharm.    307:93-102 (2006).

The invention claimed is:
 1. A pharmaceutical composition, comprising: atherapeutically effective amount of a polymalic acid-based nanoconjugateof temozolomide (TMZ), wherein the polymalic acid-based nanoconjugate ofTMZ is a compound of the formula:

or a derivative thereof, wherein the derivative is an imidazotetrazinecompound having antitumor activity; and a pharmaceutically acceptablecarrier.
 2. The pharmaceutical composition of claim 1, wherein thepolymalic-acid based nanoconjugate of TMZ is a compound of the formula:

or a derivative thereof, wherein the derivative is an imidazotetrazinecompound having antitumor activity.